Control circuit for interrupted load energization



April 1970' F. J. ANTONICH 3,506,876

CONTROL CIRCUIT FOR INTERRUPTED LOAD ENERGIZATION Filed Aug. 25, 1966 d2 V \L/ 3 1a 2 I I 1; Random 1 Random gfi j} Pulse Pulse I GeneraforGenercd-or 4! INVENTOR 77. 3 4 fimmcK .1. AA/ra/wcH fl/nAm 1 53/1189.

Afforne 95 United States Patent 3,506,876 CONTROL CIRCUIT FORINTERRUPTED LOAD ENERGIZATION Fredrick J. Antonich, 2234 S. 81st St.,West Allis, Wis. 53214 Filed Aug. 23, 1966, Ser. No. 574,401 Int. Cl.HOSb 37/02, 41/14 US. Cl. 315200 10 Claims ABSTRACT OF THE DISCLOSUREThis invention relates to a new and improved control circuit forproviding interrupted energization of a load connected to a pulsatingcurrent source and particularly to such energization of an incandescentlamp or the like to truly simulate a flickering candle.

In many applications, interrupted energization of a load may be desired.In lighting homes and business establishments, a light may be connectedin the circuit through a pulsing system to provide a flickering effectgenerally for simulating the effect of a candle. Generally, such devicesemploy a special lamp or are connected through a preset timing devicewhich turns the device on and off at a predetermined fixed rate.

The present invention is particularly directed to a control circuitwhich energizes a load at a completely random rate with the level of theenergization being controllable, if desired. Generally, in accordancewith the present invention, the lamp is connected to an alternatingcurrent source or a full wave rectified source in series with a siliconcontrolled rectifier. The rectifier means includes a triggering gateinterconnected to a no se generator which in turn is energized from theincoming power lines. The noise generator provides a random energizationof the gate and has been found to provide a highly effective randomenergization of the lamp to provide a high accurate simulation of acandle type flicker.

Generally, the input to the noise generator can be provided with avariable input control to vary the flash flicker level. Further, thecircuit can be provided with means to control and essentially vary thelight intensity from very low to that generally similar to a normallyilluminated or energized lamp.

The drawing furnished herewith illustrates preferred constructions ofthe present invention in which the above advantages and features as wellas others which will be clear from the following description of thedrawing. in the drawing:

FIG. 1 is a schematic circuit diagram of a lamp illuminating controlcircuit constructed in accordance with the present invention;

FIG. 2 is a diagrammatic view of applied voltage, the firing signals andthe lamp voltage;

FIG. 3 shows a modification to the circuit of FIG. 1; and

FIG. 4 shows a further modification to the circuit of FIG. 1.

Referring to the drawing and particularly to FIG. 1, a lamp 1 isconnected in series with a silicon controlled rectifier 2 to alternatingcurrent incoming power lines 3 of the usual distribution system or thelike. The lamp may be the well-known incandescent type employed in thehome, a Christmas tree light or the like. The illustrated siliconcontrolled rectifier 2 is a well known device having an anode 4 andcathode 5 connected in series with the lamp 1 to the power lines 3. Therectifier 2 includes a gate 6 adapted to control initiation ofconduction through the rectifier. Thus, if a positive current signal isapplied to the gate 6 simultaneously with the application of acorresponding positive polarity to the anode 4, the rectifier 2 conductsand then continues to conduct until such time as the current through theanode-cathode circuit drops below the holding current as a result of thereversal during alternate half cycles. In accordance with the presentinvention, the gate 6 is connected to a noise generator 7 through anemitter follower stage 8.

The noise generator 7 is energized through a voltage dividing network 9connected across the incoming power lines 3. Generally, the noisegenerator 7 provides a random pulse output depending upon the inputvoltage level from the voltage dividing network 9 and the random pulsesare applied to the gate 6 through the emitterfollower stage 8.

More particularly, the voltage dividing network 9 includes a diode 10 inseries with a variable resistor or potentiometer 11 connected across thepower lines 3. Current limiting resistors 12 and 13 are series connectedto the opposite sides of the potentiometer 11 in the illustratedembodiment of the invention. The tap 14 of the potentiometer 11 isconnected to provide a DC. bias supply to the noise generator 7 and tothe emitter follower stage 8. A filter capacitor 15 is connected to thetap 14 and the common line 3.

The illustrated noise generator 7 is similar to that disclosed in theElectronic Equipment Engineers Magazine of July 1964 and generallyincludes an NPN transistor 17 having a collector 18 connected to the tap14 in series with a resistor 19 and the emitter 20 connected directly tothe common line 3. A resistor 21 in series with a capacitor 22 isconnected between the collector 18 and the reference line 3. A Zenerdiode 23 interconnects the base 24 to the junction of the capacitor 22and the resistor 21. The circuit is operated near the knee of the Zenerdiode characteristic at which point the diode 23 exhibits a great amountof noise characteristics. As a result, the bias on the transistor 17 isa wide band noise signal of a generally random amplitude to provide acorresponding output at the collector 18.

The collector 18 is connected to the emitter follower stage 8 through acoupling capacitor 25. The illustrated emitter follower stage is an NPNtransistor 26 having a collector 27 connected to the tap 14 of thepotentiometer 11 and an emitter 28 connected to the common line 3 inseries with an emitter resistor 29. The base 30 is of course connectedto the noise generator 7 by the coupling capacitor and a DC. returnresistor -A connects the base to the common line 3. The emitter 28 isconnected to the gate 6 of a silicon controlled rectifier 2 to connectthe gate to cathode circuit across the emitter resistor 29. The emitterfollower 26 is connected to the incoming power lines 3 through thevoltage dividing network 9 and provides a positive output in phase withthe positive signal applied to the anode 4 of the rectifier 5. Theemitter follower stage 8 isolates the noise generator 7 from the siliconcontrolled rectifier 5 to prevent loading thereof.

The operation of the illustrated embodiment of the invention may besummarized as follows. The setting of the potentiometer 11 determinesthe voltage bias on the noise generator 7 and consequently the operatinglevel of the noise generator 7 as well as the emitter follower 26. Thenoise generator 7, as a result of the Zener diode 22, provides a wideband random amplitude output, i.e., a plurality of random pulses in theregion of the diode breakdown voltage. The series of random pulses areapplied to the gate 6 of rectifier 2 via the emitter follower stage 8and triggers the rectifier 2 at a completely random rate during thealternate half cycles of the incoming power supply.

The wave form of the power supply as applied to the lamp 1 in serieswith the rectifier 2 is shown at 31 in FIG. 2 with the amplitude shownon the vertical axis and time on the horizontal axis. The random firingpulses 32 applied to the gate 6 of rectifier 2 are shown superimposed onthe wave form 31. The firing level of the rectifier 2 is shown by thedashed horizontal line 33. The voltage applied to the lamp 1 is shown bythe separate wave form 34 in FIG. 2 having the same time base as thepower supply wave form 31.

The rectifier 2 cannot conduct during the negative half cycle of thesupply and consequently the firing pulses 32 are only effective duringthe positive half cycle. Further, only the pulses 32 which have anamplitude in excess of the firing level line 33 and which occur afterthe minimum firing angle of the rectifier 2 can trigger the rectifier toconduct in accordance with the :known operation of such rectifiers.

In the illustrated embodiment, the first firing pulse 32 of an amplitudein excess of the firing level is shown during the very initial portionof the first positive half cycle of the power supply wave form and thuswithin the minimum firing angle. Consequently, the rectifier 2 does notfire. As a result, the lamp voltage remains at zero. The subsequentfiring pulse 32 in excess of the firing level occurs after the minimumfiring angle, fires the rectifier 2 and the balance of the power supplywave form is applied to the lamp 1. Although further effective firingpulses 32 occur during the lamp conduction period, they do not cause anychange in operation because the rectifier 2 once fired continues toconduct for the remainder of the half cycle independently of gatesignal.

The operation is repeated during the subsequent positive half cycles. Asthe firing pulses 32 are of a random nature, the eifective firing pulsesduring such subsequent positive half cycles will normally differ inrelative time within the corresponding positive half cycle and thereforeprovide a different lamp conduction period as shown in wave form 34.This provides a random and varying energization of the lamp 1 to producea candle type flicker of the illumination.

In summary, lamp 1 is energized whenever a pulse is applied to the gate6 during the positive half cycle of the main power supply and is heldenergized until the end of the half cycle when the current drops belowthe holding level. As the starting point in each half cycle is random,the energization of the lamp 1 is completely random.

The output of the lamp 1 and the rate of flickering can besimultaneously adjusted through movement of the potentiometer tap 14.Thus, as the potentiometer tap 14 is moved to the upper end ofpotentiometer 11 in the illustrated embodiment of the invention, alarger voltage is applied to the noise generator 7 to cause the lamp tobe illuminated a greater portion of the time. Conversely, movement tothe other end reduces the illuminating portion during the correspondinghalf cycle to reduce the illumination level and the rate of flicker.

In FIG. 1, a diode 35 in series with a switch 36 is connected acrossrectifier 2. Diode 35 is biased to conduct the opposite half cycle whenthe rectifier is reverse biased. Closing of switch 36 therefore providesincreased energization. By closing the switch 36 and simultaneouslysetting potentiometer 11 to provide sufliciently high bias to generator7 essentially continues energization of lamp 1 without any noticeableflicker.

A modified embodiment of the invention is shown in FIG. 3 in which theoutput is a random flashing rather than a flicker as in the circuit ofFIG. 1. Corresponding elements in the embodiments of FIGS. 1 and 2 aresimilarly numbered for simplicity and clarity of explanation. In theembodiment of FIG. 3, a capacitor 37 is connected in parallel with thelamp 1. As a result, the energization of the lamp 1 is a definiterelatively slow on-oif cycle of a noticeable period rather than the veryrapid on-oif cycle of a flicker. The size of the capacitor 37, althoughnot critical, is generally related to the bias supply to the generator.Thus, it was noted that if the supply was increased, a somewhat largercapacitor was needed.

In FIG. 4, a further embodiment similar to FIG. 1 is shown employing anadditional variable illumination control.

In FIG. 4, the lamp 1 is connected to the line 3 before the flickercontrol circuit and a continuous on switch 38 is connected in parallelwith the latter to provide continuous energization if desired. Thecircuit of FIG. 1 may, of course, be similarly arranged.

Further, in FIG. 4 the alternate or negative half cycles of the powersupply are applied to the lamp 1 by a controllable dimmer circuit 39.The dimmer circuit 39 includes a controlled rectifier 40 connected inparallel with the first controlled rectifier 2 and polarized in theopposite direction. A diode 41 in series with a potentiometer 42 and acapacitor 43 are connected across the power line 3 with the junction ofthe capacitor 43 and potentiometer 42 connected in series with a currentlimiting resistor 44 to the gate 45 of the second rectifier 40. Thediode 41 is polarized in the same direction as the second rectifier 40and thus provides firing power during the appropriate half cycle. Thepotentiometer 42 and capacitor 43 provide a timing circuit with the timeat which the firing voltage is established at the junction determined bythe inserted resistance of the potentiometer 42. Thus, by adjusting thepotentiometer 42, the lamp 1 can be variously energized during thenegative half cycles to produce a minimum level of illumination uponwhich the flicker is superimposed.

In carrying out the invention, the circuit and components may be variedas desired. For example, a plurality of lamps or other loads may beseries or parallel connected. The rectifier 2 may be of the symmetricalvariety such as that sold under the trade name Triac. Further, paralleland oppositely polarized rectifiers may be provided and connected tosuitable random pulse means for functioning in the manner previouslydiscussed.

Thus, the present invention has been developed and applied in a highlysatisfactory and novel manner to provide a lamp flicker for purposes ofsimulating a candle. It can, of course, be employed in any applicaitonwhere it is desired to provide interrupted energization of a loadadapted to be controlled by a silicon controlled rectifier or othersimilar pulse controlled device.

Various modes of carrying out the invention are contemplated as beingwithin the scope of the following claims particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

I claim: 1. In an electronic lamp switching circuit for establlshing arandom power supply for intermittent and timed spaced energizing of anincandescent lamp or the like,

alternating current power connection means for connection to an incomingpower source,

a triggered electronic switch means having output means for connectionto the lamp and the power connection means and having a firing inputmeans to initiate conduction through said output means, said switchmeans conducting during alternate half cycles, and

random signal generating means connected to said input means forapplying a train of random time spaced signals to the input means totrigger said switch means during said half cycle to produce a randomtime spaced energization of the lamp.

2. The electronic switching circuit of claim 1 wherein,

said random signal generating means is a noise generator.

3. The electronic switching circuit of claim 1 wherein said triggeredswitch means is a polarized unidirectional conducting means, and saidsignal generating means includes a solid state semiconductor noisegenerator.

4. The electronic switching circuit of claim 1 wherein said triggeredswitch means is a controlled rectifier, and said signal generating meansincludes a transistor having an input circuit including a Zener diodeand supply means for operating the diode in the knee of the breakdownvoltage characteristic.

5. The electronic switching circuit of claim 1 wherein said triggeredswitch means is a triggered rectifying means and said signal generatingmeans includes a transistor having a voltage breakdown means connectedbetween the base to collector circuit, said voltage breakdown meanshaving an operating characteristic including a noise region having awide frequency wave form, and circuit means connecting the transistor tothe power connecting means for energizing said transistor and voltagebreakdown means to operate in the noise region of the voltage breakdownmeans.

6. The electronic switching circuit of claim 1 wherein said triggeredswitch means is a triggered rectifying means having a firing gate meansconnected to the signal generating means and said signal generatingmeans includes a grounded emitter transistor having a Zener diodeconnected in series with an impedance between the base to collectorcircuit, and a voltage dividing network connecting the transistor to thepower connection means for energizing said transistor and Zener diode tooperate in the noise region of the characteristic of the diode.

7. The switching circuit of claim 2 having an emitter follower stageconnected between the noise generator and the input means.

8. The switching circuit of claim 1 having a capacitor means connectedacross the output means and thereby in parallel with a load to providedefinite on-otf load power.

9. The electronic switching circuit of claim 3 having a secondunidirectional triggered conducting means and polarized to conduct inthe opposite direction and having an adjustable trigger power meansconnected to the power supply and including means to limit current flowtherethrough to the half cycle, that said first unidirectionalconducting means is reverse biased and providing a controlled actuationof the second unidirectional conducting means.

10. The electronic switching circuit of claim 9 wherein said triggerpower means is a resistor-capacitor timing circuit.

References Cited UNITED STATES PATENTS 3,070,739 12/ 1962 I-Iansen etal. 307-252 3,209,279 9/ 1965 Kambouris 331-78 3,388,269 6/1968 Bertioli328-81 3,355,625 11/1967 Ward 3 l5241 OTHER REFERENCES Applications ofElectronics, Grob and Kiuer, pp. and 51, 1960.

DONALD D. FORRER, Primary Examiner D. M. CARTER, Assistant Examiner US.Cl. X.R. 307-252, 284

